The transmission of low bit rate voiceband signals utilizing packets, while offering the prospects of significant savings in transmission and switching costs over circuit switching, has not as yet been widely used because of problems encountered in transmitting and switching encoded voiceband information via packets. One of these problems has been the random delay experienced by the packets as they progress through the transmission and/or switching network. The random delay is introduced in multiplexing and switching nodes of the network because of the queuing of packets in buffer storage units prior to transmission or switching. Unlike data, voiceband information must be decoded at a substantially fixed rate in order to maintain quality voiceband signal reconstruction. The introduction of a random delay as the packets progress through the transmission and switching networks does not allow for proper decoding unless some compensation is provided for the random delay. In order to provide this compensation, the delay must be accurately determined.
One advantageous way of providing a measure of the random delay experienced by packets as they progress through a packet switching network is the so-called time stamp arrangement disclosed in U.S. Pat. No. 4,506,358 issued to W. A. Montgomery on Mar. 19, 1985. This prior time stamp arrangement requires the use of two packet header fields associated with updating the time stamp value in a packet network mode. A first field contains the so-called packet network node. A first field contains the so-called received time stamp value upon entering the network node and the second field is used to carry the so-called packet arrival time through the network node. Upon exiting the network node, the values in time stamp field and the packet arrival time field are combined with a local timing signal value to obtain a new updated time stamp value. The calculation of the updated time stamp value is performed entirely upon exiting the network node which requires the use of the two header fields. The use of the additional arrival time field is undesirable because it requires additional equipment and control, and uses additional signal bandwidth.